Deep athletic field compaction, the number one enemy of turf grass, poses assorted problems from poor drainage to dry surface soil and knotty grass, etc. Most fields have a compacted “plow layer” just below the reach of aerators.
Until recently, turf managers were left with two options:
- Surface aeration, which helped in the 2-5” root zone, but didn’t address deep ground water flows, especially if the ground was really hard.
- Deep-ripping the field, which had the unfortunate consequence of destroying the surface.
A new approach uses a high-pressure air discharge under the compacted layer. A machine with a 1” point drives the point up to 6’ deep using hydraulics and a pneumatic jack hammer. When the air is suddenly released the blast fractures the soil in a cone shape, originating at the point of discharge and radiating upward to the surface. The diameter of the cone at the soil surface ranges from 10-16’ or greater, depending on the depth of discharge, soil type, and pressure.
To loosen a rectangular field, it is first measured and then the discharge points are laid out in a pattern so that all points are equidistant from the adjacent discharge point; a large field may have up to 1,000 deep blasting points. The distance between holes is determined by trial discharges to determine the diameter of fractures from the discharge point.
At the time of discharge, the ground heaves and settles back. Ground radar shows many fractures in the soil; the machine leaves a 1” dia hole in the field surface which is difficult to find once the machine is moved. Each deep blasting hole will hold approximately 60-80 gallons of liquid which indicates the amount of new volume created in the earth. Upon slicing a cross-section at the depth of the discharge point, no void is created and the area of fracture is very loose, almost as if an explosion was set off.
The depth of discharge generally ranges from 25-30”, which means the plow layer of compacted soil is broken in multiple places and water can again move both upward and downward. The surface of the field remains on grade while the deep compaction has been eliminated.
Amazingly, this procedure allows loosing of old tree roots without root damage and for arborist to pump many gallons of tree food/supplement into the tree feeding area.
The deep blasting technique is new and offers a tool that turf managers have not had available to them. It solves a problem that has plagued the industry since people played games on fields.